1. Technical Field
The present invention relates to new kaolin products and their preparation and use.
The invention relates to a binder mix in particular, which typically contains a hydraulically hardening binder and a pozzolanically reacting admixture.
The invention further relates to a process for manufacturing calcinated kaolin and a process for manufacturing a hardened binder mass.
2. Background Information
Metakaolin can be used as an additive of cement. Accordingly, the U.S. Pat. No. 6,027,561 describes a composition that contains cement and a highly active pozzolan that contains metakaolin. This is manufactured by means of treating kaolin thermally, elutriating it in water and drying the slurry by spray drying, whereby small agglomerated beads with a diameter of at least 10 microns are formed. They are formed from particles, the size of which (d50) is 5 microns or less. A known dispersing agent can be added into the metakaolin. As fine-grained pozzolan generally requires a greater amount of water, the purpose of the known solution is to provide a product, which has no negative effects on the fluidity or the water demand of concrete. The beads consist of metakaolin microparticles (70-100%) and dispersing agents and other additives (0-30%). In this way, the fluidity of cement can be improved compared to a case where fine-grained pozzolan is used.
Other patents, which use metakaolin as additives of cement include U.S. Pat. Nos. 5,976,241, 5,958,131, 5,626,665, 5,122,191 and 5,788,762, the latter including a versatile overview of the use of metakaolin and its advantages as an additive of cement. A common feature for all the solutions is the use of metakaolin as such, whereby its pozzolanic properties are utilized.
Microspheres consisting of various materials have been used as additives of cement. An example of such an application is the solution disclosed in US patent application 20010047741, wherein a porous substance can be, for example, volcanic ash or hollow ceramic microspheres or combinations thereof. The purpose behind the use of these microspheres is to obtain the advantage of an essentially lighter-weight substance combination. The density of the porous additive is 0.5-1.2 g/cm3, preferably 0.9-1.1 g/cm3. The size of the porous particles is 20-120 microns (micrometres).
In some cases, the spheres that are used to lighten concrete have closed surfaces, and efforts have been made to actually minimize the amount of water absorbed by them. On the other hand, large light expanded clay aggregates, which have also been used to lighten concrete and to also bring water to the concrete matrix, are so large that their relatively low strength constitutes the weakest ling in the concrete matrix.
Patent literature has also dealt with the adjustment of the amount of water during the hardening reaction of cement. Accordingly, the U.S. Pat. No. 5,948,157 discloses an admixture, the surface of which is treated so that it has a transient hydrophobic property, whereby it will not deliver water, when the admixture is added into the mix, but will later on change so that the travel of water during the hardening reaction of the mixture is possible. The additive can either react with the mixture during hardening or by means of intermediary reaction products or by physically binding itself to the mix. The additive can be any substance, the surface properties of which can be changed transiently. In a preferred application, the additive is silicate, which by nature is slightly hydrophilic. The silicate can be formed from a reactive material. It is preferably formed from a pozzolanic and hydraulic material or the mixtures thereof. The treating agent can be an organic oxide that has at least three carbon atoms. In can also be a surface-active agent that includes a hydrophobic component, which has an organic oxide with 3 carbon atoms. The treating agent covers at least part of the surface of the additive and gives it a transient hydrophobic property, but does not react with it. The purpose is that the effect of the treating agent is valid only for the time of treating the mixture and, after this, its effect starts to decrease, whereby the additive can participate in reactions with the mixture.
U.S. Pat. No. 4,095,995 deals with the manufacture of light concrete. In order to avoid the entry of water into the porous aggregate, when manufacturing light concrete, an additive is brought onto the surfaces of the aggregates, forming, together with the cement slurry, a gel-like protective layer, which only has a limited permeability to water. When coating the aggregates, a dry additive is used, which contributes to the creation of a bonding between the cement and the aggregates. The said additive is a polyethylene oxide with a high molecular weight.
Adding water by means of the particles in the concrete matrix during the hardening reaction of concrete, which can be used to decrease autogenous contraction, is dealt with in the application publication WO 0102317, wherein the said particles are of organic polymer, ‘hydrogel’.
The manufacture and use of round inorganic granules for dyeing concrete is considered, among others, in the U.S. Pat. No. 5,882,395.
Although the number of patents related to the admixtures of concrete and the control of hardening is fairly extensive, as a whole, the solutions mentioned above generally only deal with some single phenomena related to the properties of concrete, and they have neither been capable of considerably improving the manufacturing processes of cast concrete products, nor shortening the manufacturing times, nor providing concrete with better mechanical and chemical properties.